I think you definitely can, but the degree of your fandom may not be as intense if you spread it out among multiple teams. Shannon (TheHockeyGuy) on YouTube is a noted big fan of the Canucks, Bruins, and the Stars (in that order, interestingly enough).
Personally, I've had second favourite teams, but I care about them maybe 5% as much as the Canucks, so it's not really fair to say I'm a fan of them.